Apple captures the lion's share of mobile phone profits because of two reasons.
1. They sell a lot of iPhones.
2. iPhones are high-end phones.
If Samsung sold as many Galaxy S3/Note 2 devices as Apple sold iPhones, then Samsung would be getting a comparable share of the profits.
Samsung, however, chooses to manufacturer and sell low- and mid-tier smartphones which carry lower profits. Apple chooses not to sell in that market ... Aside from selling one and two year old models.